This invention relates to use of naphthalenic compounds as effective bait toxicants for their use in the control of termites.
Damage in the United States attributable to subterranean termites is now estimated to be in excess of one billion dollars a year. All wooden or wood-containing structures are potentially affected, including homes, outbuildings, fences, utility poles, railway sleepers, boats, bridges, retaining walls and even living trees. Since their introduction to the United States within the last half-century, Formosan subterranean termites (FST), Coptotermes formosanus (Shiraki), have become one of the most destructive pests in the contiguous United States. Reasons for this include their massive colonies which can contain tens of millions of individuals, their ability to attack several species of living trees, and their high level of reproduction.
The most successful existing methods for control of subterranean termites are preventive rather than remedial. These include barrier treatments to structures and the preemptive treatment of wood materials with chemicals to prevent termite attack. These methods, however, have drawbacks. Physical barriers are not compatible for retrofitting on many existing constructions and may not be completely effective, and chemical treatments are only partially effective and last only about five years.
Low toxicity baits utilizing growth regulators have shown success in reducing damage caused by subterranean termites, with diflubenzuron and hexaflumuron having been particularly effective in suppressing colonies of C. formosanus and Reticulitermes spp. Bait matrices utilized for the baits have consisted of cardboard, filter paper, pine wood, pure cellulose, and recently the use of a nutritionally based matrix. Depending on the species of termite, these matrices have shown to be effective toxicant carriers. Chen et al. (Naphthalene in Formosan Termite Carton Nests; Journal Agricultural Food Chemistry, Vol. 46, No. 6, 1998) disclose the presence of naphthalene in termite carton nests and postulated that it might constitute a unique chemical defense strategy for Formosan termites. Grace et al. (Evaluation of the Termite Resistance of Wood Pressure Treated with Copper Naphthenate; Forest Products Journal, Vol. 43, No. 11/12, November/December 1993) teaches that copper naphthenate is not only toxic to termites but is also highly repellent to them.
While various methodologies and compositions exist for the monitoring and control of termites, there remains a need for the creation of improved tools in this area.
Therefore, it is an object of this invention to provide alternative compounds as bait active ingredients effective as toxicants for termites.
Yet another object is to provide compositions and methods for the effective control of termite populations.
We have discovered that termites may be more effectively controlled through use of naphthalenic compounds in matrices at fairly low concentrations. These compounds work as an attractant for chemical systems which are toxic to termites. A termite matrix containing nutritionally requisite components enhances its usefulness as a bait and an aggregant for termites. The invention is premised on Applicants"" discovery that termites aggregate and feed on food sources that contain naphthalenic compounds.
Termites for which the naphthalene and naphthalene derivatives of this invention are useful include all termite species belonging to the families Rhinotermitidae and Kalotermitidae, preferably Coptotermes formosanus, Reticulitermes flavipes (Kollar) and Reticulitermes virginicus. 
The nutritionally based matrix may also be used as a highly effective carrier for enhancing the delivery of these termite toxicants for the purpose of destroying substantial numbers of termites and thus inhibiting termite damage to cellulosic structures such as buildings and trees.
Methods of making termite-preferred matrices of this invention are also provided comprising mixing the various components to form a toxicant containing food.
Methods of killing termites are also provided comprising placing a toxin-containing matrix in a termite habitat upon which the termites will preferentially feed in place of other environmentally-available food sources. The methods preferably also include placing hydrated, water-retaining materials, also referred to herein as water-retention agents, within the termite bait matrix or in the area immediately surrounding the termite matrix to provide a degree of humidity to the immediate area which can be detected by termites to serve as a second means of attracting them.
A termite aggregant comprising a hydrated water-retention agent contained within a termite-accessible container is also provided. The termite-accessible container refers to a container or coating which retains moisture inside but which termites can enter.
Naphthalenic compounds incorporated into cellulose-based matrices for the control of termites have been developed. Low concentrations of these chemicals are sufficient to kill native and Formosan termites colonies in field conditions. Naphthalenic compounds are considered to be any of those that possess a base structure of naphthalene. These chemicals can be used in baiting systems as a novel approach to reduce the amount of toxins required to kill termites. The matrix composition comprises cellulose, water, and naphthalene derivatives and termite-preferred nutrients.
The cellulose may be supplied by means of any cellulose-containing material, preferably having at least 50% to greater than 95% cellulose, so long as it does not include chemicals which are repellant to termites. Such usable materials include commercially available cellulose, wood, paper, and cardboard, and are preferably in particulate form for ease of mixing with the other ingredients of the matrix. Sawdust may be used from any plant source but is preferably from woods preferred by termites such as aspen, sitka spruce, maple, birch, sweet gum and related woods or any such species possessing a low content of feeding deterrent chemicals as determinable by means well known in the art. Alternate sources of sawdust, while usable, may contain chemicals in amounts that reduce the utility of such sawdust materials due to either repellant or toxic effects.
The degree to which the presence of a particular component causes termites to prefer a food over other foods not containing the component, or containing greater or lesser amounts thereof, may readily be assessed using methods known in the art.
The matrix further comprises naphthalenic compounds present in amounts ranging from about 10 ppm to about 500 ppm. Usable compounds are seen to include N-hydroxynaphthalimide (NHA), 1,8-napthalimide and sodium, magnesium, potassium and calcium salts thereof and copper naphthenate and zinc naphthenate.
Subterranean termites prefer moist foods. To be more attractive than other available foods in the environment, the formulation of this invention should be preferably moist. Enough water should be used to allow mixing of the matrix material, and/or completely hydrate the particulate or solid cellulose materials and to provide excess water to maintain a humid environment. In general about three-fourths by weight of the matrix should be water, but this may vary with the water content ranging from about 20% to about 90% by weight of the composition.
A water-retention agent capable of absorbing water and releasing it slowly to the environment can be used to ensure an acceptable moisture level in the matrix material as well as to serve as another means for termite aggregation. Examples of such materials include agar and polyacrylamide, but may include any substance not otherwise possessing a repellant effect. Examples of preferred usable materials include the polyacrylamide graft copolymer such as Terrawet(copyright) T-400 Aquawet (Terrawet Company, San Diego, Calif.), which can absorb and retain up to a thousand times their own weight in water. These materials should be hydrated, preferably fully-hydrated, with the addition of at least thirty times their weight in water containing the water-soluble naphthalene derivatives, such as NHA. The hydrated water-retaining materials may be mixed with the matrix.
The inventors have discovered that termites are attracted during their foraging to high humidity conditions, preferably at least about 80% humidity, and more preferably at least about 90% humidity. Thus, moisture-retaining material as described above is preferably placed in the immediate environment of the bait matrix to provide a humidity readily detectable by, and attractive to, termites. In a preferred embodiment in which a polyacrylamide graft copolymer such as Terrawet(copyright) 400 Aquawet is used as the water-retaining agent, it may be placed in the area of a termite bait or monitoring station at an application rate effective for eliciting an aggregant response, that is, from about 1 g to about 10 g (dry weight) per square foot. The hydrated-polyacrylamide, preferably hydrated to a NHA-water: polymer weight ratio of at least about 30:1, with a final concentration of NHA of 900 ppm, can be injected into the soil around the bait station by pressure using commercially available injectors, preferably to a radius around the bait matrix of at least about 2.5 cm, or placing it on the base of the station or inside of the above ground station or in the cracks of walls and trees or other locations susceptible to termite infestation. Other water-retaining agents as described above can alternatively be used, adjusting ratios to achieve 80% to 90% humidity as will be readily apparent to those skilled in the art. The bait container is made from a material such as paraffin, beeswax, polyurethane foam, styrofoam and fibrous casing tubes.
Naphthalenic compounds may be used to retard extreme deterioration of wood interceptors and to congregate termites to its immediate environment for purposes of monitoring the size and presence of termite populations, e.g., by observing termites and counting or otherwise estimating the number of termites present by measuring the consumption of wood interceptors. Typical monitoring strategies utilize approximately one bait station per 10-15 linear feet. The significantly faster response of termites to treated pine wood as compared to untreated pine wood results in enhanced monitoring efficacy. Additionally, these chemicals may be used alone or in combination with active secondary toxicants used in bait matrices such as streptomycin sulfate, rifampicin, albendazole, neomycin sulfate, sorbic acid, antimycotics, benzofenyl ureas, imidacloprid, hydroximethanon, juvenile hormone mimics and used in combination with preferred wood such as maple, sitka spruce, birch, douglas fir, red gum, yellow poplar, white pine or yellow pine wood to extend the period of termite activity at the monitoring site.
The matrix materials of this invention, may be encased in materials or containers which are water-retentive such that they substantially prevent evaporation of the moisture in the food, but which are vapor-permeable to a degree sufficient to allow termites to detect odors coming from the matrices.